WO2007135974A1 - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

Disclosed is a nonaqueous electrolyte secondary battery comprising a positive electrode containing an active material which adsorbs and desorbs lithium ions, a negative electrode containing an active material which adsorbs and desorbs lithium ions, a separator arranged between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The separator contains a material having an electron-withdrawing substituent. The nonaqueous electrolyte contains a nonaqueous solvent and a solute dissolved therein, and the nonaqueous solvent contains at least one substance selected from the group consisting of fluorine-containing aromatic solvents, fluorine-containing cyclic carbonic acid esters and fluorine-containing cyclic carboxylic acid esters. By using the separator and the nonaqueous electrolyte in combination, lowering of the rate characteristics of the battery can be suppressed even when the battery is stored at high voltage and high temperature.

Description

 Specification

 Nonaqueous electrolyte secondary battery

 Technical field

 [0001] The present invention relates to a separator and a non-aqueous electrolyte used in a non-aqueous electrolyte secondary battery, particularly a non-aqueous electrolyte secondary battery.

 Background art

 [0002] Currently, research on lithium ion secondary batteries having high voltage and high energy density has been actively conducted for non-aqueous electrolyte secondary batteries. For lithium ion secondary batteries, lithium-containing transition metal oxides such as LiCoO are generally used as positive electrode active materials.

 2

 A carbon material is used as a negative electrode active material, and a porous film made of polyethylene or polypropylene is used as a separator. A non-aqueous electrolyte generally includes a non-aqueous medium and a solute dissolved therein. Examples of non-aqueous solvents include cyclic carbonates, chain carbonates, and cyclic carboxylates. Examples of solutes include lithium hexafluorophosphate (LiPF) and lithium tetrafluoroborate (LiBF). It is used.

 6 4

 [0003] Conventionally, in order to improve battery characteristics, attempts have been made to improve the positive electrode active material, the negative electrode active material, the separator, and the nonaqueous electrolyte. For separators, for example, the following improvements have been made!

 In Patent Document 1, in order to further improve battery safety during short-circuiting or abnormal use, a porous fluororesin film such as polytetrafluoroethylene (PTFE), a polyethylene film, or a polypropylene film is used. It has been proposed to use separators with multiple layers. In Patent Document 1, since the separator includes a fluorine resin film having a high melting point, the separator can be prevented from melting during abnormal heat generation. For this reason, the safety of the battery can be further improved.

[0004] Patent Document 2 proposes to use a separator including two layers having different pore diameters in order to further improve the safety of a battery using metallic lithium as a negative electrode active material. The layer with the smaller pore size suppresses dendritic growth of metallic lithium, thereby suppressing internal short circuit during charging and discharging and the accompanying ignition. Patent Document 2 discloses a polytheto There is disclosed a separator in which a lafluoroethylene membrane and a membrane having a small pore diameter that also has polypropylene strength are laminated.

 [0005] On the other hand, for nonaqueous electrolytes, for example, the following improvements have been made.

 In Patent Document 3, the cycle characteristics are improved by adding fluorinated benzenes to the nonaqueous electrolyte.

[0006] Patent Document 4 proposes to use monofluoroethylene carbonate as a nonaqueous solvent for a nonaqueous electrolyte. In Patent Document 4, since a stable coating derived from monofluoroethylene carbonate is formed on the negative electrode, the cycle characteristics can be improved.

 Patent Document 1: Japanese Patent Laid-Open No. 5-205721

 Patent Document 2: JP-A-5-258741

 Patent Document 3: Japanese Patent Laid-Open No. 2005-340026

 Patent Document 4: Japanese Patent Application Laid-Open No. 2004-063432

 Disclosure of the invention

 Problems to be solved by the invention

 [0007] When the lithium-containing transition metal oxide is stored at a high voltage and a high temperature, elution of the metal constituting the lithium-containing transition metal oxide occurs severely. For this reason, metal atoms eluted from the lithium-containing transition metal oxide are deposited on the negative electrode, which increases the impedance of the negative electrode or causes the separator to be clogged. Therefore, a battery including a lithium-containing transition metal oxide as a positive electrode active material has a reduced rate characteristic after storage.

 [0008] Even when the non-aqueous solvent contains fluorinated benzenes proposed in Patent Document 3 or monofluoroethylene carbonate proposed in Patent Document 4, the above lithium-containing transition metal oxidation The elution of metal atoms from objects cannot be suppressed! For this reason, similarly to the above, the rate characteristic after storage is lowered.

 Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery that can reduce a decrease in rate characteristics during storage, particularly when stored at high voltage and high temperature.

 Means for solving the problem

[0010] The nonaqueous electrolyte secondary battery of the present invention comprises an active material that absorbs and releases lithium ions. A positive electrode containing; a negative electrode containing an active material that occludes and releases lithium ions; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte. The separator includes a material containing an electron-withdrawing substituent. The non-aqueous electrolyte includes a non-aqueous solvent and a solute dissolved therein. The non-aqueous solvent includes at least one first solvent selected from the group consisting of a fluorinated aromatic solvent, a fluorinated cyclic carbonate, and a fluorinated cyclic carboxylic acid ester. The non-aqueous solvent preferably includes at least one selected from the group consisting of a fluorine-containing aromatic solvent and a fluorine-containing cyclic carbonate. The material containing the electron-withdrawing substituent preferably contains a fluorine atom. The material is preferably polytetrafluoroethylene. The separator preferably further contains an inorganic filler.

 [0011] It is preferable that a reduction-resistant film or a reduction-resistant layer containing an inorganic filler is provided between the separator and the negative electrode.

[0012] The amount of the first solvent is preferably 10% by volume or more of the non-aqueous solvent.

[0013] The active material contained in the positive electrode preferably contains Li [Ni Mn] 0.

 1/2 3/2 4

 [0014] The present invention also relates to a system including the nonaqueous electrolyte secondary battery and a charger for charging the nonaqueous electrolyte secondary battery, wherein a charge end voltage in the charger is set to 4.3 to 4.6V. The invention's effect

 [0015] In the present invention, the material constituting the separator includes an electron-withdrawing substituent.

In such a material, since electrons are delocalized, electrons are more difficult to be extracted and oxidation resistance is improved. Therefore, it is possible to suppress the oxidation / decomposition of the separator. Furthermore, since the non-aqueous solvent contains at least one solvent selected from the group consisting of a fluorine-containing aromatic solvent, a fluorine-containing cyclic carbonate, and a fluorine-containing cyclic carboxylate, a separator is used. It is possible to improve the wettability of the nonaqueous electrolyte. For this reason, the voltage is leveled over the entire electrode group, and it is possible to prevent acid / acid decomposition of the non-aqueous solvent. One cause of the deterioration in the rate characteristics of the battery is from the positive electrode active material to other than lithium. It is considered that this metal atom is eluted as a cation into the non-aqueous electrolyte, and the metal is deposited on the negative electrode. In the present invention, even when the battery is stored at high voltage and high temperature, the separator is separated. Oxidative decomposition of non-aqueous solvent can be suppressed. Therefore, it is possible to suppress that electrons generated during oxidative decomposition move to metal atoms (other than lithium) contained in the positive electrode active material and the metal atoms become force thiones and dissolve in the nonaqueous electrolyte. . Therefore, even when the battery is stored at a high voltage and high temperature, it is possible to suppress a decrease in the rate characteristics of the battery.

 Brief Description of Drawings

 FIG. 1 is a longitudinal sectional view schematically showing a cylindrical non-aqueous electrolyte secondary battery produced in an example.

 FIG. 2 is a block diagram showing a configuration of a charger incorporating the nonaqueous electrolyte secondary battery of the present invention.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in detail.

 The non-aqueous electrolyte secondary battery of the present invention comprises a positive electrode containing an active material that absorbs and releases lithium ions, a negative electrode that contains an active material that absorbs and releases lithium ions, and is interposed between the positive electrode and the negative electrode. A separator and a non-aqueous electrolyte. Ceno routers include materials that contain electron withdrawing substituents. The nonaqueous electrolyte includes a nonaqueous solvent and a solute dissolved therein. The non-aqueous solvent includes at least one first solvent selected from the group consisting of a fluorine-containing aromatic solvent, a fluorine-containing cyclic carbonate, and a fluorine-containing cyclic carboxylate.

[0018] Generally, in a lithium ion secondary battery, a separator having polyethylene (PE) or polypropylene (PP) force is used. However, since polyethylene and polypropylene have low acid resistance, when a battery including a separator having such material strength is stored at high voltage and high temperature, the separator is oxidatively decomposed. At that time, electrons generated by the acid decomposition of the metallic nuclear separator other than lithium in the positive electrode active material are received and reduced. The metal atoms that receive the electrons are eluted from the positive electrode active material as metal cations. The low acid resistance of polyethylene and polypropylene is thought to be due to the fact that many hydrogen atoms are easily extracted in the molecule. [0019] In order to suppress the oxidative decomposition of the separator, a material containing an electron-withdrawing substituent in the molecule, such as polytetrafluoroethylene (PTFE) and polytetrafluoroethylene (PCTFE), is used. It is effective. Due to the strong electron withdrawing properties of halogen atoms, electrons are delocalized in PTFE and PCTFE, which constitute the separator, making it more difficult for the electrons to be pulled out and improving acid resistance.

 [0020] However, a separator including a material containing an electron-withdrawing substituent has a strong polarity and thus is difficult to wet with a non-aqueous electrolyte. If the separator has a portion that is not wetted by the nonaqueous electrolyte, the voltage (potential difference) between the positive electrode portion and the negative electrode portion that face each other across the portion is locally increased. When the voltage increases in this manner, the nonaqueous solvent undergoes oxidative decomposition under high temperature storage, and electrons generated by the oxidative decomposition move to metal atoms other than lithium contained in the positive electrode active material. This causes a new problem that the positive electrode active material force metal cations are eluted.

 [0021] In order to prevent the acid-decomposition of the separator and the non-aqueous solvent as described above, the non-aqueous solvent, the fluorinated aromatic solvent, the fluorinated cyclic carbonate, and the fluorinated cyclic carboxylic acid ester are used. It is very effective that the group power contains at least one selected first solvent and the separator contains a material containing an electron-withdrawing substituent. Since the first solvent contained in the non-aqueous solvent has an action of lowering the surface tension of the non-aqueous solvent, the wettability of the separator containing a material containing an electron-withdrawing substituent to the non-aqueous electrolyte is improved. For this reason, a local voltage rise is suppressed and the voltage is leveled in the whole electrode plate group. Therefore, even when the battery is stored at a high voltage and a high temperature, the oxidative decomposition of the nonaqueous solvent can be suppressed. Further, the separator used in the present invention has high acid resistance because the material constituting the separator contains an electron-withdrawing substituent. Therefore, even when the battery is stored at a high voltage and a high temperature, it is possible to suppress the decomposition of the acid in the separator.

 Both effects as described above can prevent the positive electrode force metal cation from eluting and suppress the deterioration of rate characteristics.

[0022] Note that Patent Documents 1 and 2 are also used as a membrane force separator having a PTFE force. However, using only a membrane with PTFE strength, metal cations from the positive electrode active material are eluted by oxidative decomposition of the nonaqueous solvent. Therefore, the rate characteristics of the battery after storage Decreases.

 [0023] Even when the nonaqueous electrolyte contains a fluorinated benzene as in Patent Document 3, and when the nonaqueous electrolyte includes monofluoroethylene carbonate as in Patent Document 4, the separator is used. The elution of metal cations due to the positive electrode active material force due to the acid / acid decomposition of the metal cannot be suppressed. Therefore, also in this case, the rate characteristics of the battery after storage are deteriorated.

 [0024] The material constituting the separator includes an electron-withdrawing substituent. Examples of electron-withdrawing substituents include F Cl CN SO CO COO CF

 2 3

 As the material containing an electron-withdrawing substituent, a polymer containing an electron-withdrawing substituent is preferred. For example, polytetrafluoroethylene, polychloroethylene, tetrafluoroethylene perfluoro Fluoroalkyl butyl ether copolymer, tetrafluoroethylene monohexafluoropropylene copolymer, polyamide, polyimide, polyamideimide, polyetherimide, polyarylate, polysulfone, polyethersulfone, polyetheretherketone, polyethylene Examples thereof include terephthalate, polybutylene terephthalate, acrylo-tolyl-styrene-acrylate copolymer, and a polymer containing an acrylonitrile unit.

 Separator is a material that has a substituent that contains fluorine such as 1F or 1CF in the molecule.

 Three

 It is preferable to contain. Since fluorine atoms have a high electron withdrawing property, the acid resistance of the separator becomes higher and the acid decomposition can be further suppressed.

 [0025] Among the above materials, a fluoropolymer such as polytetrafluoroethylene (PTFE) is preferable. Polytetrafluoroethylene contains four fluorine atoms with high electron-withdrawing properties in the repeating unit. Therefore, in polytetrafluoroethylene, electrons are delocalized on fluorine atoms. Therefore, the electrons are extracted from the polytetrafluoroethylene and the acid resistance is remarkably improved.

 [0026] The separator is more preferably an insulating layer containing a material containing an electron-withdrawing substituent and an inorganic filler. Such an insulating layer includes an inorganic filler and thus has high reduction resistance. Therefore, the reductive decomposition of the separator as described later can be prevented.

[0027] The separator is an insulating layer containing a material containing an electron-withdrawing substituent and an inorganic filler. In some cases, the material containing an electron-withdrawing substituent is not particularly limited, and among these, a polymer containing an acrylo-tolyl unit is preferable. In the polymer, it is preferable that the amount of atalonitrile unit is 20 mol% or more. Examples of the polymer containing an acrylonitrile unit include polyacrylonitrile, polyacrylonitrile-modified rubber, alicyclic-tolyl monostyrene mono acrylate copolymer and the like.

 [0028] By using a polymer containing an acrylonitrile unit as the material, the dispersibility between the material and the inorganic filler in the insulating layer can be improved, and reduction decomposition of the separator can be further suppressed.

 [0029] The amount of the inorganic filler is preferably 80 to 99% by weight of the insulating layer. If the amount of the inorganic filler is less than 80% by weight, the voids inside the insulating layer may decrease and the lithium ion conductivity may decrease. If the amount of the inorganic filler exceeds 99% by weight, the strength of the insulating layer itself may be lowered.

 [0030] Examples of inorganic fillers include alumina, titer, zircoure, magnesia, silica, and the like.

 [0031] When the separator includes the insulating layer, the separator may be composed of only the insulating layer. Alternatively, the separator may include, in addition to the insulating layer, a porous film having a material strength known in the art.

 [0032] The thickness of the separator is preferably 0.5 to 300 μm. This is the same even when the separator is composed of the insulating layer as described above.

 [0033] The separator including the material containing an electron-withdrawing substituent is preferably arranged so as not to be in direct contact with the negative electrode. While the separator has high oxidation resistance, the reduction resistance tends to slightly decrease. For this reason, when the negative electrode potential is greatly reduced, the portion of the separator that contacts the negative electrode may be easily reduced.

 [0034] In order to prevent reduction of the separator containing the material containing an electron-withdrawing substituent, a reduction-resistant film or a reduction-resistant layer containing an inorganic filler is disposed between the negative electrode and the separator. It is preferable.

[0035] Examples of the reduction-resistant film include a polyethylene film and a polypropylene film. The reduction-resistant layer is, for example, a layer containing an inorganic filler and a predetermined polymer. And so on. The reduction-resistant layer may be formed on the surface of the negative electrode facing the separator, or may be formed on the surface of the separator facing the negative electrode. As the inorganic filler, the above materials can be used. The type of polymer contained in the reduction resistant layer is not particularly limited. For example, when a separator made of a material containing an electron-withdrawing substituent such as a fluoropolymer is used, a reduction-resistant layer can be provided between the negative electrode and the separator. In this case, the insulating layer as described above can be used as the reduction-resistant layer.

 [0036] The thickness of the reduction-resistant layer containing the reduction-resistant film and the inorganic filler is preferably 0.5 to 25 µm. If the thickness of the reduction-resistant film and the reduction-resistant layer is less than 0.5 m, for example, when the non-aqueous electrolyte secondary battery is a wound electrode group, the pressure at the time of winding is reduced. As a result, the reduction-resistant film or the reduction-resistant layer may be crushed and the separator and the negative electrode may come into contact with each other. Therefore, the effect of suppressing reduction of the separator may be insufficient. If the thickness of the reduction-resistant film and the reduction-resistant layer is greater than 25 m, the direct current resistance is too large and the output characteristics may be degraded.

 [0037] An example of a method for manufacturing a separator is described below.

 For example, a polymer containing an electron-withdrawing substituent is mixed with an organic solvent, the polymer is melted and kneaded, extruded, and then subjected to stretching, removal of the organic solvent, drying, and heat setting. A separator can be obtained.

 For example, a separator can be obtained by the following method.

 First, a polymer and a good solvent for the polymer are mixed to prepare a polymer solution. The polymer solution as a raw material can be prepared, for example, by dissolving the polymer in a predetermined solvent by heating. The solvent is not particularly limited as long as it can sufficiently dissolve the polymer. Examples thereof include aliphatic or cyclic hydrocarbons such as nonane, decane, undecane, dodecane, and liquid paraffin, or mineral oil fractions having boiling points similar to those of these hydrocarbons. In order to improve the stability of the gel-like molded product obtained after extrusion molding, it is preferable to use a non-volatile solvent such as liquid paraffin.

[0038] The dissolution by heating may be performed with stirring at a temperature at which the polymer is completely dissolved in the solvent. However, it may be carried out while uniformly mixing in an extruder. When the polymer is dissolved while stirring in a solvent, the heating temperature varies depending on the polymer and solvent used, but is usually

140-250. C range.

[0039] When dissolving in the extruder, first, the polymer is supplied to the extruder and melted. The melting temperature varies depending on the type of polymer used. The melting point of the polymer is preferably 30 to 100 ° C.

 Next, a predetermined solvent is supplied to the molten polymer. In this way, a solution containing the molten polymer can be obtained.

[0040] Next, this solution is extruded into a sheet form from a die of an extruder, and then cooled to obtain a gel-like composition. When a polymer solution is prepared in an extruder, the solution may be extruded through a die or the like from the extruder, or the solution is moved to another extruder and passed through the die or the like. You can push it out.

 [0041] Next, by cooling, a gel-like molded product is formed. Cooling is accomplished by cooling the die or by cooling the gel sheet. The cooling is preferably performed at a rate of at least 50 ° CZ to 90 ° C or less, more preferably 80 to 30 ° C. As a method for cooling the gel sheet, a method of directly contacting a cooling medium such as cold air or cooling water, a method of contacting a roll cooled by a refrigerant medium, or the like can be used. Of these, the method using a cooling roll is preferred.

 [0042] Next, the gel-like molded product is biaxially stretched to obtain a molded product. Stretching is performed at a predetermined magnification by heating the gel-like molded product and using a normal tenter method, roll method, rolling, or a combination of these methods. Biaxial stretching may be either longitudinal or transverse simultaneous stretching or sequential stretching, but simultaneous biaxial stretching is particularly preferable.

[0043] The molded product obtained above is washed with a cleaning agent to remove the remaining solvent. Cleaning agents include volatile solvents such as hydrocarbons such as pentane, hexane, and heptane, chlorinated hydrocarbons such as salt methylene and tetrasalt carbon, and fluorides such as trifluoromethane. Ethers such as hydrocarbon, jetyl ether and dioxane can be used. These may be used alone or in combination of two or more. These cleaning agents are appropriately selected according to the solvent used for dissolving the polymer. [0044] Examples of the method of cleaning the molded product include a method of immersing the molded product in a predetermined cleaning agent to extract the residual solvent, a method of showering the cleaning product on the molded product, or a method of combining these. Can be mentioned. The molded product is preferably washed until the residual solvent in the molded product is less than 1% by weight.

 [0045] Thereafter, the molded product is dried to remove the cleaning agent. The drying can be performed using a method such as heat drying or air drying.

 [0046] Finally, a high-strength microporous membrane separator can be obtained by heat-setting the molded product after drying at a temperature of 100 ° C or higher.

 [0047] The first solvent includes at least one selected from the group consisting of a fluorine-containing aromatic solvent, a fluorine-containing cyclic carbonate, and a fluorine-containing cyclic carboxylate.

 Fluorine-containing aromatic solvents include, for example, fluorobenzene, 1,2-difluorobenzene, 1,2,3 trifluorobenzene, 1,2,3,4-tetrafluorobenzene, pentafluorobenzene, hexafluoroolefin Benzene, 2-funoleorotolenene, and a 1, a 2, a trifluorotoluene. Of these, fluorobenzene and hexafluorobenzene are preferred.

 [0048] Examples of the fluorine-containing cyclic carbonate include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, and trifluoropropylene carbonate. Of these, fluoroethylene carbonate and trifluoropropylene carbonate are preferable.

[0049] Examples of the fluorine-containing cyclic carboxylic acid ester include: a fluoro-γ-butyrolatathone, e, —difunoleol γ-butarate rataton, —funoleoro _Ί -valerolataton, and α, a-difluoro-γ-valerolataton.

[0050] Among the above, the first solvent preferably contains at least one selected from the group force consisting of a fluorine-containing aromatic solvent and a fluorine-containing cyclic carbonate. These solvents can greatly reduce the surface tension of the nonaqueous electrolyte. Accordingly, the wettability of the separator containing the material containing the electron-withdrawing substituent to the non-aqueous electrolyte is improved, the local voltage rise is suppressed, and the voltage is leveled. For this reason, even when the battery is stored at a high voltage and a high temperature, the oxidative decomposition of the nonaqueous solvent can be remarkably suppressed. [0051] Among these, as the first solvent, it is more preferable to use at least one selected from the group consisting of fluorobenzene, hexafluorobenzene, fluoroethylene carbonate, and trifluoropropylene carbonate.

 [0052] The amount of the first solvent is preferably 10% by volume or more of the non-aqueous solvent, more preferably 20% by volume or more. When the amount of the first solvent is less than 10% by volume, the effect of reducing the surface tension of the non-aqueous solvent is weakened. For this reason, the wettability of the separator containing a material containing an electron-withdrawing substituent to the non-aqueous electrolyte becomes non-uniform, and oxidative decomposition of the non-aqueous solvent may occur due to a local voltage increase. When the first solvent contains two or more kinds of the solvents, the total amount of them should be 10% by volume or more.

 [0053] The amount of the first solvent is preferably 50% by volume or less of the nonaqueous solvent, more preferably 20% by volume or less. In the case of a fluorine-containing cyclic carbonate and a fluorine-containing cyclic carboxylate, these solvents are high dielectric constant solvents and have a high viscosity. Therefore, when these solvents exceed 50% by volume of the non-aqueous solvent, the lithium ion conductivity of the non-aqueous electrolyte is lowered, and as a result, the rate characteristics of the battery may be lowered. Fluorine-containing aromatic solvents themselves are difficult to dissociate lithium salts such as LiPF. Therefore, fluorine-containing

 6

If the aromatic solvent exceeds 50% by volume of the non-aqueous solvent, the lithium salt may be precipitated. In the case where the first solvent comprises a fluorinated cyclic carbonate or a fluorine-containing cyclic carboxylic acid ester, a fluorinated aromatic solvent, the upper limit of the amount of first solvent to exceed 50 body product _^0/0 Also good.

 [0054] The non-aqueous solvent preferably contains a second solvent other than the first solvent. Examples of the second solvent include cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters. Here, examples of the cyclic ester carbonate include propylene carbonate (PC) and ethylene carbonate (EC). Examples of the chain carbonate include jetyl carbonate (DEC), ethinoremethinolecarbonate (EMC), and dimethenorecarbonate (DMC). Examples of the cyclic carboxylic acid ester include γ-petite rataton (GBL) and γ-valerolatatone (GVL).

The amount of the second solvent is preferably 90% by volume or less of the nonaqueous solvent, more preferably 60% by volume or less. [0055] In the present invention, a group strength comprising a separator containing polytetrafluoroethylene or a separator containing an electron-withdrawing substituent and a inorganic filler, a fluorine-containing aromatic solvent, and a fluorine-containing carbonate ester. A combination with a non-aqueous electrolyte containing at least one non-aqueous solvent selected is preferred.

 Among them, a separator containing a material containing an electron-withdrawing substituent and an inorganic filler, and a group consisting of a fluorine-containing aromatic solvent and a fluorine-containing carbonate, is selected and contains at least one non-aqueous solvent. A combination with a water electrolyte is more preferred. A separator containing an electron-withdrawing substituent and an inorganic filler, and a group force consisting of fluorobenzene, hexafluorobenzene, fluoroethylene carbonate, and trifluoropropylene power-at least one selected A combination with a nonaqueous electrolyte containing a nonaqueous solvent is particularly preferred.

[0056] As the solute dissolved in the non-aqueous solvent, a solute common in the field can be used. For example, LiPF, LiCIO, LiBF, LiAlCl, LiSbF, LiSCN, LiCF SO, LiCF

 6 4 4 4 6 3 3 3

CO, Li (CFSO), LiAsF, LiBCI, lower aliphatic lithium carboxylate, LiCl, Li

 2 3 2 2 6 10 10

 Br ,: chloroborane lithium such as LiI, Li B CI, bis (1,2-benzenediolate (2

 2 10 10

 —) — O, 0,) Lithium borate, bis (2, 3 Naphthalenediolate (2—) — O, 0,) Lithium borate, bis (2, 2, — Biphenyl-diolate (2—) — O , 0,) lithium borate, bis (5 fluoro-2-olate 1 benzenesulfonic acid-O, 0,) borate salts such as lithium borate, lithium bistetrafluoromethanesulfonate imido ((CF SO) NLi), tet

 3 2 2 Lifluoromethanesulfonic acid nonafluorobutane sulfonic acid imidolithium (LiN (CF SO

 Three

) (C F SO)), lithium bispentafluoroethanesulfonate imide ((C F SO) NLi

2 4 9 2 2 5 2 2

) And other imide salts can be used. These may be used alone or in combination of two or more.

[0057] The nonaqueous electrolyte preferably contains a cyclic carbonate having at least one carbon-carbon unsaturated bond. This is because such a cyclic carbonate is decomposed on the negative electrode to form a film having high lithium ion conductivity, and therefore, the charge / discharge efficiency can be increased. The amount of the cyclic carbonate having at least one carbon-carbon unsaturated bond is preferably 10% by volume or less of the nonaqueous solvent. [0058] Examples of cyclic carbonates having at least one carbon-carbon unsaturated bond include vinylene carbonate, 4-methylbinylene carbonate, 4,5-dimethylvinylene force-bonate, 4-ethyl vinylene carbonate, 4, 5— Examples include jetyl vinylene carbonate, 4-propyl vinylene carbonate, 4,5-dipropyl vinylene carbonate, 4-phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl vinylene carbonate, and dibutylene ethylene carbonate. . These may be used alone or in combination of two or more. Among these, at least one selected from the group power of bilene carbonate, butyl ethylene carbonate, and dibule ethylene carbonate is preferable.

 [0059] Further, the non-aqueous electrolyte may contain a known benzene derivative that decomposes during overcharge to form a film on the electrode and inactivate the battery. As the benzene derivative, a compound having a phenyl group and a cyclic compound group adjacent to the phenyl group is preferable.

. As the cyclic compound group, a fluorine group, a cyclic ether group, a cyclic ester group, a cycloalkyl group, a phenoxy group and the like are preferable. Specific examples of the benzene derivative include hexylbenzene, biphenyl, diphenyl ether and the like. These may be used alone or in combination of two or more. However, the content of the benzene derivative is preferably 10% by volume or less of the non-aqueous solvent.

[0060] The positive electrode includes, for example, a positive electrode current collector and a positive electrode active material layer carried thereon. The positive electrode active material layer includes a positive electrode active material capable of inserting and extracting lithium ions, a binder, a conductive agent, and the like.

 Examples of the positive electrode active material include Li CoO, Li NiO, Li MnO, Li Co Ni O, Li x 2 x 2 x 2 x y 1-y 2 x

Co M O, Li Ni M O, Li Mn O, and Li Mn M O (M is Na, Mg, Sc ゝ y 1-y z x 1-y y z x 2 4 x 2-y y 4

 It is at least one selected from the group consisting of Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, and x = 0 to l.2, y = 0 to 0. 9, z = 2. 0 to 2.3 3) can be used! These may be used alone or in combination of two or more. Note that the X value, which indicates the molar ratio of lithium, is a value immediately after the preparation of the active material, and increases or decreases due to charge / discharge.

[0061] In particular, since a battery having a high voltage of about 5V can be obtained, Li [Ni Mn] 0 is preferably used.

 3/2 4

 [0062] The negative electrode includes, for example, a negative electrode current collector and a negative electrode active material layer carried thereon. The negative electrode active material layer includes a negative electrode active material capable of inserting and extracting lithium ions, a binder, and a conductive agent as necessary.

 Examples of the negative electrode active material include graphite such as natural graphite (such as flake graphite) and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, carbon Fibers, metal fibers, alloys, lithium metals, tin compounds, silicides, and nitrides can be used.

 [0063] Examples of the binder used for the positive electrode and the negative electrode include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and tetrafluoroethylene monohexafluoropropylene. A polymer (FEP), a vinylidene fluoride hexafluoropropylene copolymer, or the like is used. Here, it is preferable that the binder added to the positive electrode contains a fluorine atom. The binder added to the negative electrode preferably does not contain a fluorine atom.

 [0064] As the conductive agent included in the electrode, for example, carbon blacks such as graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and metal fiber are used. .

 [0065] For the positive electrode current collector, for example, a powerful sheet such as stainless steel, aluminum, or titanium is used. For the negative electrode current collector, for example, a sheet having strength such as stainless steel, nickel and copper is used. The thickness of the positive electrode current collector and the negative electrode current collector is not particularly limited, but is generally 1 to 500 μm.

 [0066] In the normal operation state, the end-of-charge voltage of the nonaqueous electrolyte secondary battery of the present invention is preferably set to 4.3 to 4.6V. That is, in a system (for example, a mobile phone or a personal computer) equipped with the nonaqueous electrolyte battery of the present invention and a charger for charging the battery, the end-of-charge voltage in the charger is 4.3 to 4.6 V. Preferably it is set.

FIG. 2 shows a block diagram of an exemplary configuration of a charger that controls the charging of the battery. The charger shown in Fig. 2 is also equipped with a discharge control device. In this charger, the nonaqueous electrolyte secondary battery 30 of the present invention and the current detector 31 are connected in series. A voltage detector 32 is connected in parallel to a circuit in which the battery 30 and the current detector 31 are connected in series.

 Further, the charger includes input terminals 36a and 36b for charging the battery 30, and output terminals 37a and 37b connected to the device. The charger also includes a switching switch 35 connected in series with the battery 30. The switch 35 is switched to the charge control unit 33 side during charging, and is switched to the discharge control unit 34 side during discharging.

[0068] When a positive electrode active material such as LiCoO is used, the higher the end-of-charge voltage, the higher the positive electrode active material

 2

 Increased quality expansion. For this reason, the nonaqueous electrolyte easily enters the electrode, and the contact property between the positive electrode and the nonaqueous electrolyte is improved. Therefore, the local voltage rise at the electrode is suppressed and the voltage is leveled.

 When the end-of-charge voltage is lower than 4.3 V, the positive electrode active material does not expand so much that the non-aqueous electrolyte does not enter the electrode so much that the charging reaction proceeds more on the electrode surface, causing a local voltage increase. Arise. For this reason, the nonaqueous solvent may be oxidatively decomposed, and metallic force thione may be eluted from the positive electrode active material. When the end-of-charge voltage is higher than 4.6 V, the local voltage rise can be suppressed, but the voltage is too high, so that oxidative decomposition of the non-aqueous solvent occurs and the metal cation may elute in the active material power. is there.

 Example

[0069] Example 1

 (Battery 1-22)

 (i) Preparation of non-aqueous electrolyte

 Dissolve LiPF at a concentration of 1. OmolZL in the non-aqueous solvent shown in Table 1 to obtain a non-aqueous electrolyte.

 6

 1-22 were prepared. Here, in Table 1, the abbreviations of the first solvents used are as follows.

 FB: Fluorobenzene

 DFB: 1, 2—Difluorobenzene

 TriFB: l, 2, 3—Trifluorobenzene

TeFB: l, 2, 3, 4-tetrafluorobenzene PFB: Pentafluorobenzene

 HFB: Hexafluorobenzene

 FT: 2-Fluorotoluene

 TFT:, a, α trifluorotoluene

 FEC: Fluoroethylene carbonate

 DFEC: Diphnoreo mouth ethylene carbonate

 TriFEC: trifluoroethylene carbonate

 TeFEC: Tetrafluoroethylene carbonate

 TFPC: trifluoropropylene carbonate

 FGBL: a-Funoleor γ-Buchiguchi Rataton

DFGBL: a, a Jifunoreoro _Ί Buchirorataton

 FGVL: a—Funoleor γ—Valerolataton

DFGVL: a, a- Jifunoreoro one _Ί - Barerorataton

[0070] Abbreviations of the second solvent used are as follows.

 EC: ethylene carbonate

 EMC: Ethyl methyl carbonate

 DMC: Dimethylol carbonate

 DEC: Jetinorecarbonate

[0071] (ii) Separator

 A separator made of polytetrafluoroethylene (PTFE) (BSPO 105565-3 manufactured by Gore-Tex) was used. The separator thickness is 54 m and its porosity is 61% o

 [Iii] Production of positive electrode plate

85 parts by weight of lithium cobaltate powder, 10 parts by weight of acetylene black as a conductive agent, and 5 parts by weight of polyvinylidene fluoride resin as a binder were mixed. This mixture was dispersed in dehydrated N-methyl-2-pyrrolidone to prepare a slurry positive electrode mixture. This positive electrode mixture was applied to both surfaces of a positive electrode current collector (thickness: 15 m) that also became an aluminum foil, dried and rolled to obtain a positive electrode plate (thickness: 160 m). [0073] (iv) Production of negative electrode plate

 100 parts by weight of artificial graphite powder, 1 part by weight of polyethylene rosin as a binder, and 1 part by weight of carboxymethyl cellulose as a thickener were mixed. An appropriate amount of water was added to this mixture and kneaded to prepare a slurry-like negative electrode mixture. This negative electrode mixture was applied to both sides of a negative electrode current collector (thickness: 10 m) made of copper foil, dried and rolled to obtain a negative electrode plate (thickness: 160 μm).

[0074] (V) Manufacture of cylindrical batteries

 A cylindrical battery as shown in Fig. 1 was created.

 A positive electrode plate 11, a negative electrode plate 12, and a separator 13 disposed between the positive electrode plate 11 and the negative electrode plate 12 were wound in a spiral shape to produce an electrode plate group. The electrode plate group was housed in a nickel-plated iron battery case 18. One end of the positive electrode lead 14 made of aluminum was connected to the positive electrode plate 11, and the other end of the positive electrode lead 14 was connected to the back surface of the sealing plate 19 that was conducted to the positive electrode terminal 20. -One end of the negative electrode lead 15 made of the gasket was connected to the negative electrode plate 12, and the other end of the negative electrode lead 15 was connected to the bottom of the battery case 18. An upper insulating plate 16 is provided above the electrode plate group, and a lower insulating plate 17 is provided below the electrode plate group. A predetermined amount of the non-aqueous electrolyte 1 (not shown) prepared as described above was poured into the battery case 18. The opening end of the battery case 18 was caulked to the sealing plate 19 via the gasket 21, and the opening of the battery case 18 was sealed to complete the battery 1. The design capacity of battery 1 was 1500 mAh. In the following examples, the battery design capacity was set to 1500 mAh.

 [0075] Batteries 2 to 22 were obtained in the same manner as Battery 1, except that nonaqueous electrolytes 2 to 22 were used instead of nonaqueous electrolyte 1.

[Comparative Example 1]

 Polyethylene was used in a mixed solvent of ethylene carbonate (EC) and ethylmethyl carbonate (EMC) (volume ratio 1: 4) using 1. Non-aqueous electrolyte A in which LiPF was dissolved at a concentration of OmolZL.

 6

 Comparative battery 1 was obtained in the same manner as battery 1, except that a separator (a hypopore made by Asahi Kasei Chemicals Co., Ltd., thickness: 20 μm) that also has a styrene (PE) force was used.

[0077] <Comparative Example 2>

Separator with high PE strength (Hypore made by Asahi Kasei Chemicals Co., Ltd., thickness 20 μm) A comparative battery 2 was obtained in the same manner as the battery 1 except that.

[0078] <Comparative Example 3>

 Comparative battery 3 was obtained in the same manner as battery 9, except that a separator having high PE strength (Hypore made by Asahi Kasei Chemicals Corporation, thickness 20 μm) was used.

[0079] <Comparative Example 4>

 In a mixed solvent of EC and EMC (volume ratio 1: 4), 1. dissolve LiPF at a concentration of OmolZL.

 6 Comparative battery 4 was obtained in the same manner as battery 1 except that nonaqueous electrolyte A was used.

[0080] [Evaluation]

 (a) Measurement of the amount of metal deposited on the negative electrode after storage

 The batteries 1 to 22 and the comparative batteries 1 to 4 manufactured as described above were charged at a constant voltage of 4.3V. The charged battery was stored at 85 ° C for 72 hours.

 Thereafter, the battery after storage was disassembled, the central part of the negative electrode plate was cut into a size of 2 cm × 2 cm, and the obtained fragment was washed 3 times with ethyl methyl carbonate.

[0081] Next, an acid was added to the fragment and heated to dissolve the fragment. The insoluble matter was filtered off, and the volume was determined to prepare a measurement sample. This measurement sample was measured using an ICP emission spectrometer (VARIA

Using N VISTA-RL, the amount of metal eluted from the positive electrode and deposited on the negative electrode (in this case, the amount of Co) was quantified. The results are shown in Table 1. In Table 1, the amount of deposited metal (metal deposition amount) is converted to the amount per unit weight of the negative electrode.

[0082] (b) Capacity recovery rate

 First, each battery is charged at 20 ° C at a constant current of 1050 mA until the battery voltage reaches 4.3 V, and then charged at a constant voltage of 4.3 V for 2 hours and 30 minutes. 'Used for constant voltage charging. Next, the charged battery was discharged at a discharge current value of 1500 mA (1 C) until the battery voltage dropped to 3.0 V, and the discharge capacity before storage was determined.

[0083] Next, the discharged battery was charged as described above. The charged battery was stored at 85 ° C for 72 hours.

The battery after storage was first discharged at 20 ° C with a current value of 1C, and then further discharged with a current value of 0.2C. Next, the discharged battery is charged as described above at a constant current of 1050 mA until the battery voltage reaches 4.3 V, and then charged at a constant voltage of 4.3 V for 2 hours and 30 minutes. did. After this, the charged battery was discharged at a current value of 1 C until the battery voltage dropped to 3. OV. The discharge capacity at this time was defined as a recovery capacity after storage.

 The value obtained as a percentage value of the recovery capacity after storage with respect to the discharge capacity before storage was defined as the capacity recovery rate after storage. The results are shown in Table 1.

 Table 1 also shows the types of separators used.

[0084] [Table 1]

[0085] From the results of batteries 1 to 22, the non-aqueous solvent contains the first solvent, and the separator has a polytetrafluoroethylene force containing an electron-withdrawing substituent. It can be seen that the amount of deposited metal decreases and the capacity recovery rate after storage is good. The By using a PTFE separator containing an electron-withdrawing substituent in the molecule, the oxidative decomposition of the separator itself is suppressed. Further, when the non-aqueous solvent contains a fluorine-containing cyclic compound, the wettability of the separator to the non-aqueous electrolyte is improved, and the oxidative decomposition of the non-aqueous electrolyte can be suppressed. It is presumed that both of these effects suppressed the positive electrode force from leaching out metal cations, and the above results were obtained.

 [0086] When the non-aqueous solvent contains at least one selected from the group consisting of a fluorine-containing aromatic solvent and a fluorine-containing cyclic carbonate, storage characteristics (capacity recovery rate) were excellent. The fluorine-containing aromatic solvent and the fluorine-containing cyclic carbonate can greatly reduce the surface tension of the nonaqueous electrolyte. For this reason, the wettability of the separator to the non-aqueous electrolyte is improved, the local voltage rise is suppressed, and the voltage is leveled in the electrode plate group. Therefore, it is considered that the oxidative decomposition of the non-aqueous solvent was remarkably suppressed even when the battery was stored at a high voltage and high temperature.

 <Example 2>

 (Battery 23-39)

 Batteries 23 to 39 were produced in the same manner as the battery 9 except that a separator having material strength as shown in Table 2 was used.

 Using these batteries, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate after storage were measured in the same manner as described above. Table 2 also shows the results for battery 9.

[0088] In Table 2, the abbreviations for the material of the separator are as follows.

 PCTFE: Polychlorinated trifluoroethylene

 PFA: Tetrafluoroethylene perfluoroalkyl butyl ether copolymer

FEP: Tetrafluoroethylene monohexafluoropropylene copolymer

 PA: Polyamide

 PI: Polyimide

 PAI: Polyamideimide

 PEI: Polyetherimide

 PAR: Polyarylate

PSF: Polysulfone PES: Polyethersulfone

 PEEK: Polyetheretherketone

 PET: Polyethylene terephthalate

 PBT: Polybutylene terephthalate

 ASA: Acrylonitrile / Styrene / Atylate Copolymer

 PAN-containing insulating layer: Insulating layer that also works with polymer (PAN) containing acrylonitrile units and alumina

 PVDF-containing insulating layer: Insulating layer made of polyvinylidene fluoride (PVDF) and alumina

PES-containing insulating layer: insulating layer comprising polyethersulfone (PES) and alumina [0089] These separators were prepared as described above.

 Various polymers were dissolved in a predetermined organic solvent to prepare polymer solutions. This solution was extruded into a sheet from the die of the extruder. Next, the extruded sheet was cooled at a cooling rate of 50 ° CZ to 90 ° C or lower to obtain a gel composition.

 Next, the gel-like molded product was biaxially stretched at a predetermined magnification to obtain a molded product. The resulting molded product was then washed with a detergent until the residual solvent was less than 1% by weight of the molded product. The cleaning agent was appropriately changed depending on the type of solvent used. Thereafter, the molded product was dried to remove the cleaning agent.

 Finally, the dried molded product was heat set at a temperature of 100 ° C or higher to obtain a separator.

 These separators had a thickness of 54 μm and a porosity of 61%.

[0090] The PAN-containing insulating layer, the PVDF-containing insulating layer, and the PES-containing insulating layer were produced by the following procedure.

[0091] and alumina 970g median diameter 0. 3 μ m, polyacrylonitrile modified rubber binder (Nippon Zeon (Ltd.) BM- 720H (solid content concentration of 8 wt _^0/0)) and 375 g, an appropriate amount of N-methyl 2-Pyrrolidone was stirred with a double arm kneader to prepare a paste. This paste was applied to both negative electrode active material layers at a thickness of 20 / zm, dried, and then further dried at 120 ° C for 10 hours under vacuum and reduced pressure to form a PAN-containing insulating layer. did.

[0092] Instead of polyacrylonitrile-modified rubber binder, polyvinylidene fluoride (solid content concentration 8 PVDF-containing insulating layer and PES-containing insulating layer were formed in the same manner as described above except that polyethersulfone (solid content concentration: 8% by weight) was used.

[0093] [Table 2]

[0094] From Table 2, even when the type of material constituting the separator is changed, if the material includes an electron-withdrawing substituent, the amount of metal deposited on the negative electrode after storage decreases, and It can be seen that the recovery rate is a good value. This is presumably because, as described above, the decomposition of both the separator and the non-aqueous solvent was suppressed, and it was possible to prevent the positive-force metal cations from eluting.

[0095] Among these, a battery including a separator having a material strength including a fluorine atom in the composition 9 And 24 to 25, the capacity recovery rate with a small amount of metal deposition was improved. This is thought to be because the strong electron withdrawing property of the fluorine atoms increased the acid resistance of the separator and further suppressed oxidative decomposition.

 [0096] From Table 2, the storage characteristics were particularly excellent in the case of the battery 9 in which the material constituting the separator was PTFE. Since PTFE contains four fluorine atoms in the repeating unit, electrons are delocalized in the polymer constituting the separator due to the strong electron withdrawing properties of the fluorine atoms. For this reason, it is thought that the electrons were pulled out and the oxidation resistance of the separator was particularly improved.

 [0097] Batteries 37 to 39, each having an electron-withdrawing substituent-containing polymer and an inorganic filler insulating layer, also have a high capacity recovery rate with less metal deposition compared to other batteries. O This insulating layer has a high resistance to reduction because it contains many inorganic fillers. For this reason, it is considered that the reductive decomposition of the separator was suppressed.

 In particular, the storage characteristics of the battery 37 having an insulating layer made of a polymer containing an acrylonitrile unit and an inorganic filler were particularly excellent. This is because when the polymer containing an acrylonitrile unit is contained in the insulating layer, the dispersibility of the polymer and the inorganic filler polymer in the insulating layer is excellent, and thus the effect of suppressing the reductive decomposition of the separator is enhanced. Escaped.

<Example 3>

 (Battery 40-43)

Battery 9 and Battery 37 are the same except that a reduction-resistant membrane (Hypore made by Asahi Kasei Chemicals Co., Ltd., thickness 20 m) with polyethylene (PE) force is placed between the separator and the negative electrode. Thus, batteries 40 and 42 were produced. In addition, the same as batteries 9 and 37, except that a reduction-resistant membrane (Celgard 2400, manufactured by Celgard Co., Ltd., thickness 25 m) with polypropylene (PP) force was placed between the separator and the negative electrode. Thus, for these batteries from which batteries 41 and 43 were produced, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate after storage were measured in the same manner as described above. The results are shown in Table 3. Table 3 also shows the results for battery 9 and battery 37. [0099] [Table 3]

[0100] From Table 3, the batteries 40 and 42 in which a PE-resistant reduction-resistant film is further arranged between the separator and the negative electrode and the PP-resistant reduction-resistant film between the separator and the negative electrode are shown. In batteries 41 and 43 with more membranes, the amount of metal deposited on the negative electrode after storage was less than in batteries 9 and 37. In addition, the capacity recovery rates of batteries 40 to 43 were better than those of batteries 9 and 37. This is because it is possible to prevent reduction of the PTFE and PAN-containing insulating layer separator placed on the positive electrode side by placing a film with high reduction resistance and PE strength on the negative electrode side or a film made of PP. It is thought that it was because of.

 [0101] Example 4

 (Battery 44)

 A battery 44 was produced in the same manner as the battery 9, except that a reduction-resistant layer was provided on the negative electrode. For battery 44, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate after storage were measured in the same manner as described above. The results are shown in Table 4. Table 4 also shows the results for battery 9.

[0102] [Preparation of reduction-resistant layer on negative electrode] Alumina 970g median diameter 0. 3 μ m, polyacrylonitrile modified rubber binder (Nippon Zeon's BM- 720H) N-methyl-2-pyrrolidone containing methyl-2-pyrrolidone (NMP) solution (solid content 8 wt _^0/0) A paste was prepared by stirring 375 g and an appropriate amount of NMP in a double-arm kneader. This paste was applied onto both negative electrode active material layers of the negative electrode, dried, and further dried at 120 ° C. for 10 hours under vacuum at 120 ° C. to form a reduction-resistant layer. In each negative electrode active material layer, the thickness of the applied paste was:

[0103] [Table 4]

[0104] From Table 4, in the battery 44 in which a further layer of reduction resistance was provided on the negative electrode, the amount of metal deposited on the negative electrode after storage was less than that of the battery 9. In addition, the capacity recovery rate of the battery 44 was better than that of the battery 9. This is thought to be because the reduction of the PTFE-powered separator was prevented by providing a reduction-resistant layer on the negative electrode.

 [0105] <Example 5>

 In this example, using the battery 9, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate were measured in the same manner as described above. When performing these measurements, the end-of-charge voltage was 4.2V, 4.3V, 4.4V, 4.5V, 4.6V, or 4.7V. The results are shown in Table 5.

[0106] [Table 5] Charge capacity after storage

 Ending voltage Metal deposition amount Recovery rate

 (V) (/ g) (%)

 4.2 20 71.7

 4.3 8.8 84.1

 4.4 9.4 83.0

 4.5 11 82.3

 4.6 15 80.2

 4.7 25 68.8

[0107] From Table 5, when the non-aqueous solvent contains a fluorine-containing cyclic carbonate and a separator such as PTFE is used, the voltage during charging (that is, the end-of-charge voltage) is 4.3 to 4.6 V. By setting to, the amount of metal deposited on the negative electrode after storage is remarkably reduced, and a good capacity recovery rate can be obtained. The non-aqueous solvent contains a fluorine-containing aromatic solvent and Z or a fluorine-containing cyclic carboxylic acid ester instead of or in addition to the fluorine-containing carbonate ester, and the separator has an electron-withdrawing property other than PTFE. Even in the case of a material containing a substituent, the same tendency as above was shown.

 <Example 6>

 (Battery 45)

 Battery 45 is similar to Battery 9 except that Li [Ni Mn] 0 is used as the positive electrode active material.

 1/2 3/2 4

 Was made.

 [0109] Comparative Example 5

 Similar to Comparative Battery 1 except that Li [Ni Mn] 0 was used as the positive electrode active material, the ratio was

 1/2 3/2 4

 A comparative battery 5 was produced.

[0110] << Comparative Example 6 >>

 Similar to Comparative Battery 3, except that Li [Ni Mn] 0 was used as the positive electrode active material, the ratio was

 1/2 3/2 4

A comparative battery 6 was produced. [0111] Comparative Example 7

 Similar to Comparative Battery 4, except that Li [Ni Mn] 0 was used as the positive electrode active material, the ratio was

 1/2 3/2 4

 A comparative battery 7 was produced.

 [0112] For battery 45 and comparative batteries 5 to 7, the amount of metal deposited on the negative electrode after storage and the capacity recovery rate after storage were measured in the same manner as described above. Note that Li [Ni Mn] 0, which is a positive electrode active material, has a high discharge voltage of 4.6 V to 4.8 V with respect to lithium metal. For this reason

1/2 3/2 4

 The end-of-charge voltage in the above measurement was set to 4.9V. In measuring the amount of metal deposited on the negative electrode, the amount of Ni and Mn were quantified by ICP emission spectroscopy, and the total amount was defined as the amount of metal deposited on the negative electrode after storage.

 The results are shown in Table 6.

[0113] [Table 6]

[0114] From Table 6, even when Li [Ni Mn] 0 was used as the positive electrode active material, the non-aqueous solvent was the first.

 1/2 3/2 4

 By including a solvent and the separator contains a material containing an electron-withdrawing substituent, the amount of metal deposited on the negative electrode after storage is reduced, and a good capacity recovery rate after storage can be obtained.ゎ

 Industrial applicability

[0115] The nonaqueous electrolyte secondary battery of the present invention can suppress the deterioration of the rate characteristics even after being stored at a high voltage and a high temperature. For this reason, the nonaqueous electrolyte secondary battery of the present invention can be used, for example, as a power source for equipment that may be stored at high temperatures.

Claims

The scope of the claims

 [1] A positive electrode containing an active material that occludes and releases lithium ions, a negative electrode containing an active material that occludes and releases lithium ions, a ceno-router disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte Comprising

 The separator includes a material containing an electron-withdrawing substituent,

 The non-aqueous electrolyte includes a non-aqueous solvent and a solute dissolved in the non-aqueous solvent, and the non-aqueous solvent is composed of a fluorine-containing aromatic solvent, a fluorine-containing cyclic carbonate, and a fluorine-containing cyclic carboxylate. A non-aqueous electrolyte secondary battery comprising at least one selected first solvent.

 [2] The nonaqueous electrolyte secondary battery according to [1], wherein the nonaqueous solvent includes at least one selected from a group power consisting of a fluorine-containing aromatic solvent and a fluorine-containing cyclic carbonate.

 [3] The nonaqueous electrolyte secondary battery according to [1], wherein the material containing an electron-withdrawing substituent contains a fluorine atom.

 4. The nonaqueous electrolyte secondary battery according to claim 1, wherein the material containing the electron-withdrawing substituent is polytetrafluoroethylene.

[5] The nonaqueous electrolyte secondary battery according to claim 1, wherein the separator further contains an inorganic filler.

 6. The nonaqueous electrolyte secondary battery according to claim 1, wherein a reduction resistant layer including a reduction resistant film or an inorganic filler is provided between the separator and the negative electrode.

 7. The nonaqueous electrolyte secondary battery according to claim 1, wherein the amount of the first solvent is 10% by volume or more of the nonaqueous solvent.

 [8] The non-aqueous battery according to claim 1, wherein the active material contained in the positive electrode contains Li [Ni Mn] 0.

 1/2 3/2 4

 Denatured secondary battery.

 [9] The non-aqueous electrolyte secondary battery according to claim 1 and a charger for charging the non-aqueous electrolyte secondary battery, wherein a charge end voltage in the charger is set to 4.3 to 4.6V. System.